To synthesize siloxanes with fluorinated hydrocarbon groups, the preferred startng materials according to the state of the art are silanes, which carry these fluorinated hydrocarbon groups. The reason for this is that the addition reaction of fluoroalkyl olefins to the SiH groups of silanes is facilitated by the presence of halogen atoms, which are linked to the same silicon atom. However, the synthesis of siloxanes of the previously given structure from silanes with fluorinated hydrocarbon groups also creates difficulties, since the hydrolysis and condensation of these silanes preferentially results in the formation of cyclic siloxanes.
It is furthermore known that fluorinated hydrocarbons with olefinic double bonds may be added to the SiH group of hydrogensiloxanes. In general, this addition reaction is hindered appreciably by other hydrocarbon or siloxy substituents on the silicon atom.
Fluoroalkylsilanes or siloxanes are disclosed in the German Offenlegungsschrift No. 3,423,608. These organosilicon compounds carry norbornyl groups having fluoro or fluoroalkyl groups. These compounds are synthesized by the addition reaction of the corresponding 2-norbornene derivative to hydrogensiloxanes in the presence of platinum catalysts. This addition reaction proceeds smoothly and in a satisfactory yield. However, because of the required fluorinated norbornyl derivative and the need to use a platinum catalyst, these compounds are relativey expensive.
There continues to be a need to synthesize polysiloxane with perfluorinated alkyl groups in as simple and therefore as inexpensive a manner as possible. To this end, especially those methods come into consideration, by means of which the appropriate fluorine-containing groups can be incorporated into the completely formed backbone of the polysiloxane. This has the advantage that it is possible to start with equilibrated organopolysiloxanes and to introduce the fluoroalkyl-containing substituents only at the end of the synthesis. At the same time, the new fluoroalkyl containing groups polysiloxanes shall have the defoaming properties of this class of compounds and be as effective as possible. Especially those compounds are of interest, which make it possible to defoam preparations which contain organic solvents, such as paints or lacquers. Furthermore, products are desired, which are able to defoam crude oil. Such defoaming problems arise, for example, when crude oil is extracted from a deposit under a high pressure and low-boiling hydrocarbons escape from the crude oil after the extraction, when the pressure is released.